Not the UK, but Canada. And as 'nodisplayname' suggested, I actually did provide my yellow-book/pink-ID #, with a handwritten/typed caveat that it was not yet activated as my Thai TIN. That pink-ID# with the noted caveat, was accepted by a few Canadian financial institutes. In fact, that (approach) was pretty much what the Phuket Revenue Department branch told me when they denied my application for a Thai TIN when I applied for such. .... Possibly if i had pushed Phuket RD harder, to activate my pink-ID# as a Thai TIN, they would have activated (or they would have given me a different Thai TIN), but since they stated they saw no need to active such as a TIN yet, I saw no need to push the matter - especially given the Canadian financial institutes accepted my Thai Pink-ID# with noted caveat.